The present disclosure relates generally to industrial process control transmitters. More particularly, the present disclosure relates to housings that protect electronics and sensors used in the transmitters.
Process instruments are used to monitor process parameters, such as pressure, temperature, flow and level, of process fluids used in industrial processes. For example, process transmitters are typically employed in industrial manufacturing facilities at multiple locations to monitor a variety of process parameters along various production lines. Process transmitters include sensors that produce an electrical output in response to physical changes in the process parameter. For example, pressure transmitters include capacitive pressure sensors that produce an electrical output as a function of the pressure of a process fluid, such as water lines, chemical tanks or the like. Each process transmitter also includes transmitter electronics for receiving and processing the electrical output of the sensor so that the transmitter and process parameter can be monitored locally or remotely. Locally monitored transmitters include displays, such as LCD screens, that show the electrical output at the site of the process transmitter. Remotely monitored transmitters include electronics that transmit the electrical output over a control loop or network to a central monitoring location such as a control room. Configured as such, the process parameter can be regulated from the control room by including automated switches, valves, pumps and other similar components in the control loop.
In order to couple these electrical components with the process fluid, the components are contained in casings that can be mounted to a process fluid vessel, such as a storage tank or pipeline, with process wetted components such as flanges, manifolds, diaphragms or other transmitter mounting components. Typically, the casings comprise a module in which the sensor is mounted to interact with the process fluid, such as through a diaphragm system, and a housing in which the transmitter electronics are positioned. The housing includes a port for receiving the module and wiring from the sensor. Additionally, the housing includes an access opening for connecting the transmitter electronics to wires of a network. Alternatively, the access opening can be fitted with an antenna that allows the transmitter electronics to communicate over a wireless network. Recent advancements in technology have led to a decrease in the size of antennas, which has permitted placement of the antenna completely within the housing and rendered the access opening unnecessary. Housings are conventionally fabricated from metallic materials, which are not highly permeable to wireless signals. There is, therefore, a need for industrial process transmitter housings that are more compatible with wireless network technology.